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Marine Gen. John Allen is planning to retire rather than be re-nominated for the powerful post of NATO supreme allied commander-Europe, after White House officials forced him to step aside, a source familiar with the discussions told Fox News on Wednesday.

The source told Fox that Allen was leery of getting into a confirmation battle that would dig into the embarrassing issue of his emails with Tampa socialite Jill Kelley, but the real reason was the White House power play.

“He’s out,” the source said. “I know he is retiring. He was pushed out of the door.”

The official Pentagon announcement is expected soon.

The source also said White House officials are optimistic that after a contentious battle, former Nebraska Republican Sen. Chuck Hagel will be confirmed shortly as Defense secretary, and he can help pick a new person for the post.

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Previously, the White House was thought to be keeping the nomination open while Allen mulled whether to seek the post.

Outgoing Defense Secretary Leon Panetta said earlier in the day that he told Allen on Tuesday that Allen needs to take time to decide what is best for him and his family.

Panetta also said the administration has “tremendous confidence” in Allen.

President Obama’s first nomination of Allen expired amid an investigation of the emails between Allen and Kelley, who was connected to a scandal involving then-CIA Director Gen. David Petraeus. Allen was cleared in the investigation. But the White House purportedly had to re-nominate Allen for the post.

Fox News' Justin Fishel contributed to this report.